Several types of hand stamps are available in the commercial market. Most common are self-inking hand stamps and pre-inked hand stamps. Self-inking hand stamps contain an internal source of ink and a mechanism for inking. Thus, self-inking hand stamps include a rather large number of internal parts, and therefore may not be easy to assemble. Great efforts have been expended to develop self-inking hand stamps, which can be quickly and inexpensively assembled. One brand of high quality self-inking hand stamps is sold by MandR Marking System, Inc. of Piscataway, N.J., under the trademark IDEAL. A good example of simplified assembly for self-inking hand stamps is disclosed in U.S. Pat. No. 5,768,992, assigned to MandR Marking System, Inc.
For a variety of applications, mostly due to a smaller number of internal parts, the pre-inked hand stamps are preferable to self-inking hand stamps. Due to the absence of an internal source of ink and inking mechanism and therefore simpler construction, the pre-inked hand stamps may be less expensive and easier to assemble. To insure that a pre-inked hand stamp may create a large number of impressions before a need for re-inking arises, the marking structures of pre-inked hand stamps are made from microporous marking materials, and as such are called microporous marking structures. The microporous marking structures are usually made from suitable polymeric materials or resins (i.e., thermoplastic resins) or other open cell compositions, which include a large quantity of microscopic pores. The multiplicity of such pores allows impregnation of microporous structures with a large quantity of ink. When such microporous marking structures are impregnated with ink and used in hand stamps, thousands of impressions may be created without applying additional ink to the marking structure. The microscopic size of the pores allows the ink to escape at a controlled rate. The marking structure of a pre-inked hand stamp is called the stamp dye.
The stamp dye of a pre-inked hand stamp typically includes a marking surface and a non-marking surface. The marking surface includes raised characters of the image to be created when the hand stamp is pressed against the paper to be marked. When the marking surface of the stamp dye is placed in contact with the paper to be marked, the ink is released at a controlled rate through the surface of the marking structure. The micropores within the raised character are not sealed, allowing the ink to pass through. The pores on the rest of the surface of the stamp dye must be sealed to prevent the release of ink and the distortion of the image.
Several methods of making stamp dyes are known. These methods include for example, syntering, salt leaching and others. Also, stamp dyes may be made from gel material, salt-leached/laser etched rubber or thermal etched foam. One of the preferred methods of making stamp dyes involves cutting the microporous material with a laser. To increase the precision of the cutting process, lasers of higher power are sometimes required. It is known that use of a lower wattage laser may lead to an increase in size error.
A typical pre-inked hand stamp includes a platen, a stamp dye made of a microporous material, a case and a mechanism for moving the stamp dye between marking and non-marking position. The stamp dye is usually secured to the platen and moves along with the platen between a marking and a non-marking position. The non-marking surface of the stamp dye usually lies flat against the platen. The stamp dye has traditionally been secured to the platen by using either a mechanical securing device or an adhesive.
Several drawbacks have been associated with the use of adhesives. For example, the adhesive may work its way through from the non-marking surface of the stamp dye toward the marking surface. There, the adhesive could seal off part of the marking surface, thereby creating ink transfer problems and distorting the image. Problems have also arisen with the use of adhesives because they do not adhere well to wet surfaces. To overcome this problem, the non-marking surface of the stamp dye is typically sealed with a sealant material. The process of applying the sealant material prior to the application of a suitable adhesive can be messy and inconvenient. More importantly, the sealing of the non-marking surface prevents re-inking of the stamp dye from the rear, i.e., from the side of the non-marking surface.
Even with the large ink capacity of modern microporous materials, the stamp dye eventually runs out of ink. It is preferable to re-ink the stamp dye from the rear, i.e., from the side of the non-marking surface, because the marking surface pre-inking is messy and necessitates a temporary suspension in the use of the hand stamp. However, when the non-marking surface is sealed to allow the use of adhesive, the re-inking from the rear is impossible since the sealant closes the pores, inhibiting the absorption of ink.
The use of mechanical securing procedures does not require the use of a sealant, and thus allows re-inking from the rear. However, the use of the mechanical securing devices has also been, to date, associated with some drawbacks. The mechanical securing device is typically a ring or a ledge, which holds the edges of the marking surface of the stamp dye in the assembled position on the platen. In the prior art hand stamps, a mechanical securing device, e.g., a ring or a ledge, is usually locked on the platen in a single locking position. When the ledge is locked, the distance between the ledge and the platen is fixed and cannot be adjusted. However, the thickness of stamp dies to be used with the hand stamp varies, for example as a function of the cutting error. Therefore, some stamp dies will be held tightly, whereas others will not. To address this drawback, the majority of commercially available pre-inked hand stamps, which utilize the mechanical securing devices, commonly use additional shims to properly fit the stamp dye between the platen and the mechanical securing device. Whether the ring or the ledge fits inside the platen or outside the platen, the prior art pre-inked hand stamps usually use such shims. The use of shims leads to additional steps in the assembling process, as well as the increase in cost for the shims themselves. Also, shims may somewhat inhibit re-inking from the rear.
Therefore, there is a need for an improved pre-inked hand stamp that allows securing a stamp dye in an infinite number of positions within a desired range.
The present invention addresses this need by providing a hand stamp that allows the use of stamp dyes of various thicknesses, as well as a method of assembling such hand stamps.
In accordance with one aspect of the present invention, a hand stamp is provided which includes a case, a platen secured for movement within the case, a stamp dye which is retained adjacent to the platen, allowing the movement of the stamp dye together with the platen between a non-marking position and a marking position, and a retaining member which may be mounted on the platen in any one of a plurality of positions. In an assembled position, the stamp dye is secured adjacent to the platen. Preferably, the retaining member is directly mounted on the platen. Preferably, the retaining member is mounted in such a way that it may assume any one of an infinite number of positions between a lowermost position, where the retaining member is furthermost from the platen, and an uppermost position where it is closest to the platen. By assuming a position which corresponds to the thickness of the particular stamp dye, the hand stamp may accommodate stamp dyes of various thicknesses.
In a preferred embodiment of the present invention, the platen includes a substantially plain button surface, a top surface and a perimeter. The retaining member includes a frame, which defines an interior opening. The stamp dye, having a marking surface and a non-marking surface, is positioned with the non-marking surface adjacent to the bottom surface of the platen, and the marking surface extending through the interior opening. The interior opening allows the marking surface of the stamp dye to reach the surface to be marked.
The hand stamp of the present invention also includes one or more clips for securing the retaining member to the platen by friction. The clips extend in a direction substantially perpendicular to the bottom surface of the platen and may be part of and integral with the retaining member. The frame of the retaining member includes a ledge and a sidewall, which are integral and substantially perpendicular to each other. The ledge extends into the interior opening in the plane parallel to the bottom surface of the platen. In the assembled hand stamp, the non-marking surface of the stamp dye lies flat against the bottom surface of the platen, and the marking surface of the stamp dye and the perimeter of the marking surface of the stamp dye is arranged flat against and adjacent to the ledge.
The clips for securing the retaining member on the platen by friction fit may include a pair of flexible and resilient fingers. The fingers may extend upwardly from and be integral with the sidewall of the retaining member. The fingers are constructed in an arrangement having a broad part and a narrow part, wherein they are capable of moving toward each other so that the broad part becomes narrower. In the most preferred embodiment, the arrangement has a form of letter xe2x80x9cVxe2x80x9d.
The platen may include a platenwall, which defines the perimeter of the platen and extends in a direction substantially perpendicular to the bottom surface of the platen. When the stamp dye is inside the assembled hand stamp, it is enclosed by the platenwall. The platenwall may include one or more grooves having a width adapted for receiving the fingers of the retaining member. The grooves extend in a direction substantially perpendicular to the bottom surface of the platen. When the fingers of the retaining member are in inserted into the grooves of the platen, they are flexed toward each other and thus exert pressure in the direction opposite to the direction of their flexing, allowing the retaining member to be mounted on the platen in friction-fit arrangement.
The hand stamp according to an embodiment of the present invention may also include openings through the top and bottom surfaces of the platen for supplying ink to the stamp dye. The hand stamp may also include a handle and a shaft arranged within the case and being connected between the platen and the handle, as well as a spring for biasing the platen in the non-marking position.
In accordance with another aspect of the present invention, a part for a hand stamp is provided. The part is designed for holding a stamp dye in the assembled hand stamp. The part for hand stamp includes a platen and a retaining member mounted on the platen in any one of a plurality of positions such that a stamp dye is secured within the part adjacent to the platen.
According to an embodiment of the present invention, the retaining member may be mounted on the platen in any one of an infinite number of positions between the lowermost position and an uppermost position, whereby, upon final assembly of the hand stamp, stamp dyes of various thicknesses may be tightly secured between the platen and the retaining member by assuming the final assembled position which corresponds to the thickness of the stamp dye. The part for a hand stamp according to the present invention may also include one or more clips for mounting the retaining member on the platen in friction fit arrangement. The clips may extend vertically between the retaining member and the platen and may be part of the retaining member. The clips may also be integral with the retaining member. It is important to appreciate that other arrangements of the retaining member and the platen are possible. For example, the clips may extend from the platen or be integral with the platen. In such a case, the retaining member would include the grooves for friction fit mounting. Also, the clips may be independent from both the platen and the retaining member. One skilled in the art appreciates that all of these arrangements are within the scope of the invention.
The part for a hand stamp may include a substantially planar bottom surface, a top surface and a perimeter. The retaining member may include a frame defining an interior opening, with the frame including a ledge and a sidewall integral and substantially perpendicular to each other. The ledge may extend into the interior opening narrowing the interior opening and lie in a plane substantially parallel to the bottom surface of the platen. The part for a hand stamps according to the present invention may also include one or more clips extending in the direction substantially perpendicular to the bottom surface of the platen. The clips may include a pair of flexible and resilient fingers in an arrangement having a broad part and a narrow part. The fingers could be capable of moving toward each other to narrow the broad part. The arrangement may have a forum of letter V. Preferably, the clips extend operably from and integral with the side wall of the retaining member, with the broad part of the arrangement directed toward the platen. The platen may include a platenwall defining the perimeter of the platen and integral therewith. Preferably, the platenwall extends downward in a direction substantially perpendicular to the bottom surface of the platen. In the assembled hand stamp, the platenwall encloses a stamp dye placed therein.
To receive the fingers of the retaining member, the platen wall has one or more grooves extending in the direction substantially perpendicular to the bottom surface of the platen. When fingers are engaged in the grooves, they are flexed toward each other exerting pressure in the direction opposite the direction of their flexing, allowing the retaining member to be mounted on the platen by a friction feed mechanism. In a particularly preferred embodiment, the platen and the retaining member are rectangular, and the retaining member includes four clips. The retaining member is produced from a resilient and flexible material, preferably an appropriate plastic.
According to yet another aspect of the present invention, the method of assembling a part of hand stamp comprising a retaining member, a platen and stamp dye is provided, the method including the steps of placing the stamp dye within the retaining member so that the perimeter of the stamp dye is enclosed by the perimeter of the retaining member, arranging the platen of the retaining member so that the perimeter of the platens surrounds the perimeter of the retaining member, and applying a force to the platen to create a sufficient friction fit with respect to the retaining member, whereby the stamp dye is secured in the assembled position within the platen and the retaining member. Preferably, in this method of assembling a part of a hand stamp, the retaining member includes a frame defining interior opening and with the frame including a ledge and sidewall integral and substantially perpendicular to each other, the ledge extending and then narrowing the interior opening. Most preferably, the platen includes a substantially planar bottom surface and a top surface. In the most preferred embodiment, the platen is placed over the retaining member with the ledge being substantially parallel to the bottom surface of the platen. The most preferable embodiment includes assembling the part for the hand stamp described above.